Virtually-interfaced robotic ankle &amp; balance trainer

ABSTRACT

According to an aspect of the invention, a robotic ankle and balance training platform comprises a footplate to support a foot. The footplate is capable of rotation about an inversion/eversion axis and a plantar/dorsiflexion axis. The robotic platform further comprises an actuation system configured to apply an assistive inversion/eversion force and a resistive inversion/eversion force to the footplate and an assistive plantar/dorsiflexion force and a resistive plantar/dorsiflexion force to the footplate.

CROSS-REFERENCE(S) TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional Patent Application No. 61/730,819, filed on Nov. 28, 2012, the content of which is hereby incorporated by reference herein in its entirety.

This patent disclosure may contain material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the U.S. Patent and Trademark Office patent file or records, but otherwise reserves any and all copyright rights.

INCORPORATION BY REFERENCE

All patents, patent applications and publications cited herein are hereby incorporated by reference in their entirety in order to more fully describe the state of the art as known to those skilled therein as of the date of the invention described herein.

TECHNICAL FIELD

This technology relates generally to patient rehabilitation. In particular, aspects of this invention relate to ankle rehabilitation and balance training devices.

BACKGROUND

Due to the wide range of neurological impairments and orthopedic ankle injuries, there is a need for a device that can efficiently and accurately measure a patient's ankle strength and balance abilities as well as monitor their progress throughout therapy. There is additionally a need for a device that can be used in stable and dynamic operational modes and can utilize a virtual reality user interface for the training exercises. There is further a need for a device that can be controlled in real-time, can vary assistive and resistive forces, and analyze and provide feedback on patient performance. There is also a need for a device with diagnostic and rehabilitative capabilities.

As such, an object of one or more embodiments of the invention is to provide a robotic ankle rehabilitation device that will help patients improve their ankle balance and strength. A further object of one or more embodiments of the invention is to provide a device that can be robotically controlled, can incorporate a virtual reality user interface, and can provide diagnostic capabilities as well as objective feedback at a lower cost than its competitors. An additional object of one or more embodiments of the invention is to provide a device that can efficiently and accurately measure a patient's ankle strength and balance abilities as well as monitor their progress throughout therapy. A further object of one or more embodiments of the invention is to provide a device that can be used in stable and dynamic operational modes and can utilize a virtual reality user interface for the training exercises. An additional object of one or more embodiments of the invention is to provide a device that can be controlled in real-time, can vary assistive and resistive forces, and can analyze and provide feedback on patient performance. It is also an object of one or more embodiments of the invention to provide a device with diagnostic and rehabilitative capabilities.

SUMMARY

According to an aspect of the invention, a robotic ankle and balance training platform comprises a footplate to support a foot. The footplate is capable of rotation about an inversion/eversion axis and a plantar/dorsiflexion axis. The robotic platform further comprises an actuation system configured to apply an assistive inversion/eversion force and a resistive inversion/eversion force to the footplate and an assistive plantar/dorsiflexion force and a resistive plantar/dorsiflexion force to the footplate.

According to one or more embodiments of the invention, the robotic ankle and balance training platform further comprises an inversion/eversion frame to allow rotation of the footplate about the inversion/eversion axis; and a plantar/dorsiflexion frame to allow rotation of the footplate about the plantar/dorsiflexion axis. According to further embodiments, the inversion/eversion frame and the plantar/dorsiflexion frame are integral with the footplate. In still further embodiments of the invention, the robotic ankle and balance training platform includes sensors for measuring at least one of tensile force, compressive force, and footplate position. In one or more additional embodiments, the sensors comprise at least one pair of load cells; and at least one spring configured to assert a preload on the at least one load cell pair. In a further embodiment of the invention, the sensors comprise two load cell pairs and two springs and the load cells are located in the Anterior(A)/Posterior(P) and Medial(M)/Lateral(L) planes with respect to the ankle supported on the footplate. In additional embodiments of the invention, the robotic ankle and balance training platform includes the sensors are capable of measuring a center of pressure on the footplate. In one or more additional embodiments of the invention, the ankle and balance training platform includes sensors are capable of measuring at least one of the assistive inversion/eversion force, the resistive inversion/eversion force, the assistive plantar/dorsiflexion force, and the resistive plantar/dorsiflexion force. In one or more embodiments of the invention, the plantar/dorsiflexion axis is offset between approximately 20% and 40% of a length of the footplate from an end of the footplate. In further embodiments of the invention, the robotic ankle and balance training platform of any of further includes a mechanical stop to physically limit at least one of inversion/eversion and plantar/dorsiflexion movement of the footplate. In additional embodiments of the invention, the robotic ankle and balance training platform further comprises a first pair of shafts substantially aligned with the inversion/eversion axis, wherein capheads on the first pair of shafts are counter sunk in the inversion/eversion frame; and a second pair of shafts substantially aligned with the plantar/dorsiflexion axis, wherein capheads of the second pair of shafts are counter sunk in the plantar/dorsiflexion frame. In additional embodiments of the invention, the actuator system further comprises at least one of an inversion/eversion motor and a plantar/dorsiflexion motor. In still one or more additional embodiments of the invention, the robotic ankle and balance training platform includes a pulley assembly; a gearbox to transfer force to the footplate via the pulley assembly. In one or more additional embodiments of the invention, the robotic ankle and balance training platform further includes an encoder positioned to read at least one of an inversion/eversion position of the footplate and a plantar/dorsiflexion position of the footplate.

According to a further aspect of the invention, a robotic ankle and balance training device can include a first robotic ankle and balance training platform according to any of the previous embodiments and a second robotic ankle and balance training platform according to any of claims 1-14. In one or more embodiments of the invention, the robotic ankle and balance training device additionally includes a controller for determining a desired force for at least one of the assistive forces and the resistive forces and instructing the actuator system of at least one of the robotic platform to provide the desired force to the footplate of the at least one of the robotic platforms. In further embodiments of the invention, the robotic ankle and balance training device further comprises a sliding track, wherein the sliding track is configured to allow a distance between the first and second robotic platforms to be adjusted. Additionally, in one or more additional embodiments of the invention, the robotic ankle and balance training device further includes a stationary platform to house the first and second robotic platforms; a safety rail connected to the stationary platform; a lift-assist chair to allow use of the first and second robotic platforms in a seated or a standing position; and a virtual reality interface configured to interface with the first and second robotic platforms and provide feedback in response to at least one of a footplate orientation and a force asserted by the foot. In further embodiments of the invention, at least one of the robotic platforms actuates in response to at least one of the force asserted by the foot and the feedback from the virtual reality interface. In additional embodiments of the invention, the virtual reality interface is configured to provide visual feedback in response to a center of pressure measurement to at least one of the robotic platforms.

According to an additional aspect of the invention, method of ankle and balance training comprises measuring a range of motion of an ankle in at least four directions and in a circular motion using a robotic ankle and balance training platform; measuring a maximum exertion of the ankle in at least the four directions using the robotic platform; determining a fatigue point of the ankle at approximately 20% of the maximum exertion using the robotic platform; and detecting a weight shift of a patient using the robotic platform. In one or more further embodiments, the weight shift is detected while a footplate of the robotic platform is stationary. In one or more additional embodiments, the weight shift is detected while a footplate of the robotic platform is rotating about one or more of an inversion/eversion axis and a plantar/dorsiflexion axis.

According to a further aspect of the invention, a method of ankle and balance training comprises placing a foot on a robotic ankle and balance training platform any of the preceding embodiments and receiving a visual feedback from a visual interface based on at least one of an orientation of the foot on the robotic platform and a force asserted by the foot against the robotic platform.

These and other aspects and embodiments of the disclosure are illustrated and described below.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects and embodiments of the invention are described with reference to the following figures, which are presented for the purpose of illustration only and are not intended to be limiting.

In the Drawings:

FIG. 1 shows an Overall Virtually-Interfaced Robotic Ankle and Balance Trainer System Design according to one or more embodiments of the invention.

FIG. 2 shows a conceptual illustration of a robotic platform in accordance with one or more embodiments of the invention.

FIG. 3 shows a linear actuator utilizing vertical orientation in accordance with one or more embodiments of the invention.

FIG. 4 shows linear actuation providing motion in 2 Degrees of Freedom (DOF) using lever arms in accordance with one or more embodiments of the invention.

FIG. 5 shows a view of the footplate assembly using rotary motors to provide motion in 2 Degrees of Freedom (DOF) in accordance with one or more embodiments of the invention.

FIG. 6 shows a platform according to one or more embodiments of the invention.

FIG. 7 shows a platform using a vertical motor and universal joint drive system according to one or more embodiments of the invention.

FIG. 8 shows a platform using a half-gear mounted underneath a footplate according to one or more embodiments of the invention.

FIG. 9 shows a platform using a partial gear design and right angle gearbox according to one or more embodiments of the invention.

FIG. 10 shows a front-left view of a robotic platform according to one or more embodiments of the invention.

FIG. 11 shows a rear-right view of a robotic platform according to one or more embodiments of the invention.

FIG. 12 shows a robotic platform in an actuated position (plantarflexion and inversion) according to one or more embodiments of the invention.

FIG. 13 shows an isometric view of a footplate assembly according to one or more embodiments of the invention.

FIG. 14 shows a top view of the footplate assembly according to one or more embodiments of the invention.

FIG. 15 shows an isometric view of the footplate assembly according to one or more embodiments of the invention.

FIG. 16 shows a close-up of the peak-stress location on the footplate assembly according to one or more embodiments of the invention.

FIG. 17 show an inversion/eversion mechanical stop according to one or more embodiments of the invention.

FIG. 18 shows a plantar/dorsiflexion mechanical stop according to one or more embodiments of the invention.

FIG. 19 shows a track in accordance with one or more embodiments of the invention.

FIG. 20 shows an example of a safety harness, which can be used in accordance with one or more embodiments of the invention.

FIG. 21 shows a safety railing setup with a patient seated in a chair in accordance with one or more embodiments of the invention.

FIG. 22 shows a safety railing setup with a patient standing out of a chair in accordance with one or more embodiments of the invention.

FIG. 23 shows an example of a chair base with a hydraulic foot pump in accordance with one or more embodiments of the invention.

FIG. 24 shows exemplary design flex calculations for one or more embodiments of the invention.

FIG. 25 shows a 3D CAD image of an exemplary robotic platform support frame according to one or more embodiments of the invention.

FIG. 26 shows an image of an interior frame with both rotating frame sub-assemblies according to one or more embodiments of the invention.

FIG. 27 shows an image of the interior frame inversion/eversion sub-assembly according to one or more embodiments of the invention.

FIG. 28 shows an image of an interior frame plantar/dorsiflexion frame sub-assembly according to one or more embodiments of the invention.

FIG. 29 shows an image of plantar/dorsiflexion pulley and timing belt assembly according to one or more embodiments of the invention.

FIG. 30 shows a LabVIEW Control System for Plantar/dorsiflexion axis according to one or more embodiments of the invention.

FIG. 31 shows a block diagram representing flow of information from the user's hand to the footplate according to one or more embodiments of the invention.

FIG. 32 shows a LabVIEW control window according to one or more embodiments of the invention.

FIG. 33 shows deformation due to loading on the ball of the foot on a resized frame according to one or more embodiments of the invention.

FIG. 34 shows cap heads of shafts counter sunk into a frame according to one or more embodiments of the invention.

FIG. 35 shows load cell placement according to one or more embodiments of the invention.

FIG. 36 shows a crossbar for mounting the load cells and springs according to one or more embodiments of the invention.

FIG. 37 shows a “Sandwich” design to preload load cells according to one or more embodiments of the invention.

FIG. 38 shows a cover for an inversion/eversion encoder according to one or more embodiments of the invention.

FIG. 39 shows an inversion/eversion motor cover according to one or more embodiments of the invention.

FIG. 40 shows a slanted cover design according to one or more embodiments of the invention.

FIG. 41 shows a front view of platform and railings according to one or more embodiments of the invention.

FIG. 42 shows rear view of platform and railings according to one or more embodiments of the invention.

FIG. 43 shows a CAD design for a bench according to one or more embodiments of the invention.

FIG. 44 shows an embodiment of the invention comprising robotic platforms.

FIG. 45 shows a robotic force-plate according to one or more embodiments of the invention.

FIG. 46 shows a force-plate structure in accordance with one or more embodiments of the invention.

FIG. 47 shows a mechanism of tensile force measurement in accordance with one or more embodiments of the invention.

FIG. 48 shows a flow chart representing an exemplary collection of load cell data in accordance with one or more embodiments of the invention

FIG. 49 shows load cell calibration characteristics in accordance with one or more embodiments of the invention.

DETAILED DESCRIPTION

FIG. 1 shows a view of a Virtually-Interfaced Robotic Ankle and Balance Trainer system 100 according to one or more embodiments of the invention. According to one or more embodiments, the ankle and balance trainer system can include a stationary platform 101, which can house two robotic platforms 202. The robotic platforms include footplates for accommodating one or both feet of the user. Embodiments of the invention can also include safety features 103 and a lift-assist chair device 104. The robotic platforms 102 can move in inversion/eversion and plantarflexion/dorsiflexion motions. The two robotic platforms 102 can provide balance training as well as assistive and resistive exercise modules. The platform 101 can have extra room around the robotic platforms 102 so a patient can step forward or backward while using the robotic platforms 102 to exercise. The safety harness can be used on patients that are training in the standing position and risk falling during exercise due to poor balance. The safety railings can be in place for patients to use during sitting or standing for extra support if needed. The chair device 104 can provide the ability for the patient to train in the seated position and can have a lift assist device that can change the angle of the patient's position. The system can also include a computer-based controller with a data acquisition system and a motor control system that can calculate forces experienced during use and provide the desired resistive and active forces of the system. A description of each of these features according to one or more embodiments of the invention is described below.

Robotic Platform

FIG. 2 shows a conceptual illustration of a robotic platform 201 showing patient position in accordance with one or more embodiments of the invention. In one or more embodiments of the invention, a two degrees of freedom system can be provided that can provide and withstand torque for assisting or resisting a patient's motion during exercises. One or both footplates can be used for training purposes. In one or more embodiments, the robotic platform of the ankle and balance trainer system can include mechanical stops that restrict the range of motion of the footplate for balance training and diagnostics. One or more embodiments of the invention can also include features to the reduce cost and/or the size of a device.

In one or more embodiments, the height of the robotic platform can be ten inches or less, which can advantageously keep the height close to that of the average stair step. Many potential users of the ankle and balance trainer system in accordance with embodiments of the invention will be neurologically impaired, so situating oneself on the machine should be as easy as possible.

In one or more embodiments the robotic platform includes a multicomponent footplate in which an inner component provides a support for the user's foot as well as plantar/dorsiflexion (PFDF) about an axis, and an outer component provides inversion/eversion (INEV) about a separate axis. In further embodiments of the invention, the inner component can provide inversion/eversion about an axis and an outer component can provide plantar/dorsiflexion about a separate axis.

In one or more embodiments of the invention, a pulley-timing belt system can be used to drive the desired inversion/eversion and plantar/dorsiflexion motion. A belt and pulley can be selected based on the horsepower of the motor, speed of the shaft, and maximum torque output desired. Also, in one or more embodiments of the invention, the ratio of the pulleys can be 1:1 because the torque multiplication and speed reduction in certain embodiments can be sufficient from the gearbox alone. In other embodiments, other ratios can be used. In one or more embodiments of the invention, a contained gearbox assembly can be used to provide safe and reliable transfer of rotation to a footplate via the pulley and timing belt assembly.

FIG. 10, FIG. 11, and FIG. 12 show views of one or more embodiments of the invention, which can include a robotic footplate, where pulley and timing belt assemblies can be used for the inversion/eversion and plantar/dorsiflexion axes of rotation. FIG. 10 shows a front-left view of a robotic platform 1200 according to one or more embodiments of the invention, in which robotic footplate 1200 can comprise a footplate assembly 1201, including an inner footplate 1202 and an outer footplate 1203, shafts 1204, which can interface the inner footplate 1202 and the outer footplate 1203, a frame 1205, shafts 6806, which can interface the outer footplate 1203 and the frame 1205, and pulley and timing belt assemblies 1207, including belts 1208 and pulleys 1209, and can include gearbox assemblies 1211, which can independently transfer inversion/eversion and plantar/dorsiflexion rotation to footplates 1202 and 1203 via the pulley and timing belt assemblies 1207. As shown in FIG. 10, the shafts 1204 can be located substantially along an inversion/eversion axis and the inner footplate 1202 can rotate about an inversion/eversion axis. Further, as shown in FIG. 10, the shafts 1206 can be located substantially along a plantar/dorsiflexion axis and the outer footplate 1203 can rotate about a plantar/dorsiflexion axis. Additionally, as shown in FIG. 10, a robotic footplate 1200 can include bearings 1210 in which shafts 1206 can rotate. In further embodiments of the invention, an inner footplate can provide plantar/dorsiflexion rotation and an outer footplate can provide inversion/eversion rotation. Additionally, in further embodiments of the invention, shafts can interface an inner footplate with an outer footplate substantially along a plantar/dorsiflexion axis and other shafts can interface an outer footplate with a frame substantially along an inversion/eversion axis.

FIG. 11 shows a rear-right view of a robotic platform 1300 according to one or more embodiments of the invention, in which robotic footplate 1300 can comprise a footplate assembly 1301, including an inner footplate 1302 and an outer footplate 1303, shafts 1304, which can interface the inner footplate 1302 and the outer footplate 1303, a frame 1305, shafts 1306, which can interface the outer footplate 1303 and the frame 1305, and pulley and timing belt assemblies 1307, including belts 1308 and pulleys 1309, and can include gearbox assemblies 1311, which can independently transfer inversion/eversion and plantar/dorsiflexion rotation to footplates 1302 and 1303 via the pulley and timing belt assemblies 1307. As shown in FIG. 11, a gearbox assembly 1311 can, for example, be attached to footplate assembly 1301 to transfer inversion/eversion force and another gearbox assembly 1311 can, for example, be mounted to a frame 1305 to transfer plantar/dorsiflexion force. As shown in FIG. 11, the shafts 1304 can be located substantially along an inversion/eversion axis and the inner footplate 1302 can rotate about an inversion/eversion axis. Further, as shown in FIG. 11, the shafts 1306 can be located substantially along a plantar/dorsiflexion axis and the outer footplate 1303 can rotate about a plantar/dorsiflexion axis. As noted previously, other in other embodiments of the invention, different configurations can be used and different components can provide inversion/eversion and/or plantar/dorsiflexion motion.

FIG. 12 shows a robotic platform 1400 in an actuated position (plantarflexion and inversion) according to one or more embodiments of the invention, in which robotic footplate 1400 can comprise a footplate assembly 1401, including an inner footplate 1402 and an outer footplate 1403, shafts 1404, which can interface the inner footplate 1402 and the outer footplate 1403, a frame 1405, shafts 1406, which can interface the outer footplate 1403 and the frame 1405, and pulley and timing belt assemblies 1407, including belts 1408 and pulleys 1409, and can include gearbox assemblies 1411, which can independently transfer inversion/eversion and plantar/dorsiflexion rotation to footplates 1402 and 1403 via the pulley and timing belt assemblies 1407. As shown in FIG. 12, a gearbox assembly 1411 can, for example, be attached to footplate assembly 1401 to transfer inversion/eversion force and another gearbox assembly 1411 can, for example, be mounted to a frame 1405 to transfer plantar/dorsiflexion force. As shown in FIG. 12, the shafts 1404 can be located substantially along an inversion/eversion axis and the inner footplate 1402 and can rotate about an inversion/eversion axis. Further, as shown in FIG. 12, the shafts 1406 can be located substantially along a plantar/dorsiflexion axis and the outer footplate 1403 can rotate about a plantar/dorsiflexion axis. As noted previously, other in other embodiments of the invention, different configurations can be used and different components can provide inversion/eversion and/or plantar/dorsiflexion motion.

In one or more embodiments of the invention, the plantar/dorsiflexion axis can be located between approximately 20% to 40% of the length of a platform, and preferably at approximately 33% of the length of the platform. Such placement can improve alignment of the plantar/dorsiflexion axis with alignment of an ankle joint. In one or more embodiments of the invention, the inversion/eversion axis can be located at approximately 50% of the width of the platform. In other embodiments, the plantar/dorsiflexion axis and the inversion/eversion axis can be located in other locations along the platform.

The use of a pulley and timing belt assembly for plantar/dorsiflexion axis in certain embodiments has several potential advantages. First, it can reduce cost. The cost of a right-angle gearbox can be significantly higher than the cost of an in-line gearbox with the same ratio. In addition, the weight and the lead time can be higher for a right-angle gearbox because, at times, they are in less demand. Another advantage of a pulley and timing belt assembly can be to provide a more compact robotic footplate assembly. By choosing an in-line gearbox, the size of the motor/gearbox combination can be smaller and can be fit underneath the footplate. This can provide a simpler design for certain embodiments, as well an easier allocation of space for lateral adjustment of the robotic footplates on rails in certain embodiments.

In one or more embodiments of the invention, the design can advantageously minimize the weight of the footplate. In certain embodiments, a single slab of aluminum can be used, but the weight can be high and the weight may not be warranted for purposes of rigidity. As such, in certain embodiments, the footplate can be assembled as four pieces of aluminum that create an inner frame with two aluminum bars that go across for supporting an acrylic piece that can rest on top of that. Acrylic can be significantly lighter than aluminum and can provide a relatively high rigidity. Two support beams can be added to ensure minimal deflection in the plate with a weight of one patient (300 lbs.) on a single plate.

FIG. 6 shows a view of a robotic platform 600 according to one or more embodiments of the invention. In FIG. 6, the robotic platform 600 can comprise a footplate 601, including an inner component 602 providing plantar/dorsiflexion about a plantar/dorsiflexion axis and an outer component 603 providing inversion/eversion about an inversion/eversion axis. The inner component 602 can interface with the outer component 603 with shafts 604, and the outer component 603 can interface with the frame 605 with shafts 606. The robotic platform 600 can further include bearings 610 in which shafts 604 and 606 can rotate. The robotic platform 600 can additionally include motors 609, a drive shaft 607, and a linkage-shaft 608.

When the link such as a linkage-shaft 608 is further from an axis such as a plantar/dorsiflexion axis, the link may travel further but may use less force to provide torque. By contrast, when a link is closer to an axis, the link may travel less, but may use greater force. In one or more embodiments of the invention, the plantar/dorsiflexion motion can, for example, be at least 50° plantarflexion and 20° dorsiflexion. As such, in one or more embodiments of the invention, the front of the inner footplate can, for example, travel a total of about 9.25 inches downward and 4 inches upward. To permit a desired range of motion for a platform about the plantar/dorsiflexion axis and the inversion/eversion axis, in one or more embodiments of the invention, motors and links controlling plantar/dorsiflexion and inversion/eversion motion can be located to avoid interfere.

Additionally, since it may be desirable in some embodiments for plantar/dorsiflexion torque to be higher than inversion/eversion torque, one or more embodiments of the invention can use a direct drive system. For example, FIG. 7 shows a view of an embodiment of the invention in which a robotic platform 700 can comprise a footplate 701, including an inner component 702 providing inversion/eversion about an inversion/eversion axis and an outer component 703 providing plantar/dorsiflexion about a plantar/dorsiflexion axis. The inner component 702 can interface with the outer component 703 with shafts 704, and the outer component 704 can interface with to the frame 705 with shafts 706. The robotic platform 700 can further include bearings 710 in which shafts 704 and 706 can rotate. The robotic platform 700 can additionally include motors 709, a drive shaft 707, and a linkage-shaft 708, and a high-torque universal joint 711.

In another alternative embodiment of the invention, a partial gear such as a half gear can be secured underneath a footplate driven by a gear attached to a motor shaft. Gears can be used to increase torque and/or reduce speed. Depending on gear ratios, an input speed from a motor can be multiplied by an increase factor the output torque sees from the input torque. In many embodiments, a footplate speed of 50 rpm can be sufficient. FIG. 8 shows a view of an embodiment of the invention in which robotic footplate 1000 can comprise a footplate assembly 1001, including an inner component 1002 and an outer component 1003, shafts 1004, a frame 1005, shafts 1006, and a partial gear 1007 secured underneath the footplate assembly 1001 and driven by a gear 1008 attached to a motor shaft 1009. The inner footplate component 1002 can interface with the outer footplate component 1003 with shafts 1004, and the outer footplate component 1003 can interface with to the frame 1005 with shafts 1006. The robotic platform 1000 can further include bearings 1010 in which shafts 1006 can rotate. In one or more embodiments of the invention, a larger partial gear 1007 can be used, cutting off more than half of partial gear 1007, such that an imaginary pivot center of half gear 1007 lines up with a desired inversion/eversion axis of the footplate. This modification can increase the axis of rotation for inversion/eversion, which might otherwise be undesirably low. In one or more embodiments, bearings are selected to provide a larger range of motion so as to permit the partial gear 1007 and the gear 1008 to maintain full contact with each other when the outer footplate 1003 sees plantar/dorsiflexion. However, in an alternative embodiment depicted in FIG. 8, when the footplate is plantar/dorsiflexed and also begins inversion/eversion rotation, it is possible for the gear 1007 to disengage from the drive gear 1008.

In one or more embodiments, an inversion/eversion movement can use a partial gear, such as a half-gear or a third-gear, attached to the inversion/eversion axis on the rear of the footplate for inversion/eversion and can include a drive-gear/motor assembly mounted to the footplate for plantar/dorisflexion. FIG. 9 shows a view of an embodiment of the invention in which the robotic footplate 1100 can comprise a footplate assembly 1101, including an inner footplate 1102 and an outer footplate 1103, shafts 1104, a frame 1105, shafts 1106, and a partial gear 1107 attached to an inversion/eversion axis on the rear of the footplate 1101 and driven by a gear 1108 attached to a drive-gear/motor assembly 1109 mounted to the footplate assembly 1101. The inner footplate 1102 can interface with the outer footplate 1103 with shafts 1104, and the outer layer 1103 can interface with to the frame 1105 with shafts 1106. The robotic platform 1100 can further include bearings 1110 in which shafts 1106 can rotate. The robotic platform 1100 can additionally include a right angle gearbox 1111 to drive motion about the plantar/dorsiflexion axis.

There are several benefits to embodiments as depicted in FIG. 9 that were not provided in previous designs. For example, the motor 1109 can be situated in an open housing where it can sit on two brackets and have two brackets above it. The brackets above the motor 1109 can serve the purpose of a mechanical stop on the inversion/eversion axis to prevent over-rotation, which can help reduce risk of injury to a patient or user. An additional advantage of mounting a motor to the underside of a footplate as, for example, shown in FIG. 9, can be that it can prevent potential issues with a drive gear and a half gear disengaging by allowing a motor and a drive gear to move with plantar/dorsiflexion rotation.

In one or more embodiments of the invention, a partial gear can be approximately one-third of a gear. Using a partial gear such as a one-third gear can allow for over-rotation such that the drive gear disengages from the one-third gear to prevent the motor from continuously applying torque when the footplate cannot rotate any farther. In one or more embodiments, safety can be further enhanced by advantageously including a mechanical safety that can deactivate the motor in the event that this disengagement happens. In certain embodiments, the ratio from the drive gear to a partial gear, such as a one third gear, can be 1:1. In further embodiments, other gear ratios can be used.

In one or more alternative embodiments of the invention, linear actuators can provide direct force on the plate to provide the desired resistive and active forces. In one or more embodiments of the invention, linear actuators can be placed adjacent to the footplate and lever arms can be used to transfer force. FIG. 3 shows an embodiment of the invention that can include two vertical linear actuators 301 per footplate 302 to control plantarflexion/dorsiflexion and inversion/eversion, respectively. The amount of space below the footplate is reduced to provide a desired height by having the linear actuators 301 oriented vertically at the side of the footplate 302. Lever arms 303 provide the mechanical connection between the linear actuator and the footplate.

FIG. 4 shows a side perspective view of the vertically displaced linear actuation to illustrate the motion in 2 Degrees of Freedom (DOF) at the footplane. The motion is achieved using lever arms 403, which apply a pivoting force about a pivot point 404. Advantage of such embodiments of the invention can include improving the force applied from actuators 401 (not shown) to the footplate 402 utilizing the lever principle. However, since the levers can serve as the means to transmit the force from the actuator 401 (not shown) to the footplate 402, the lever arms 402 should generally be rigid enough to withstand significant force. Additionally, since it may be desirable to be able to adjust the stance width, the actuators 401 should generally be fixed to something that can be adjusted to different horizontal positions and that can withstand the reaction force.

In one or more alternative embodiments of the invention, rotary motors can provide force used to provide the desired resistive and active forces of the system. Rotary motors can offer a compact source of motion because they are generally rotational, whereas the motion of linear actuators is generally linear. One or more alternative embodiments of the invention can use direct drive to drive two axes of rotation directly from a drive shaft of each of two rotary motors.

In one or more embodiments of the invention, torque output can be converted from a drive shaft to a linear motion by use of a linkage-shaft attachment. FIG. 5 shows a view of the footplate assembly, including a footplate 501, using rotary motors 502 to provide motion in 2 DOF in accordance with one or more embodiments of the invention. Torque output can be converted from a drive shaft 503 to a linear motion by use of a linkage-shaft attachment 504. An advantage of such embodiments can be that the force, if applied at the edge of the footplate 501, can act over a moment arm that can be a distance from the shaft contact with the footplate 501 to the axis of rotation. This can effectively multiply the force over that distance. The drive shafts 503 of the motors 502 can be connected to one end of a linkage that can transfer force to a vertical shaft attached to the footplate. The base of the footplate 501 can also seated on a ball joint 505 atop a support structure 506 that can allow for a wide range of motion. The motors 502 can be oriented on a base plate 507 and connected to the footplate 501. Each motor 502 can provide motion in 1 DOF, such that the combination of motors can provide inversion/eversion and plantarflexion/dorsiflexion forced motion. The support structure 506 can minimize direct force on the shafts 504 driving motion, which can allow for more efficient transfer of force from the motors 502. In such embodiments of the invention, it may be desirable for the motors 502 to provide force to the foot plate 501 while keeping the overall size of the system small. In this alternative embodiment, an input torque from a motor can, for example, be 50 N-m along with a crank arm of 0.0762 meters and a footplate moment arm of 0.1016 meters, and the upper end of the footplate angle can, for example, have approximately 30 N-m of applied torque.

For certain applications, it may be desirable for a robotic platform to provide enough force to counter act a patient's weight, while still providing a desired minimum range of motion for exercises. According to one or more embodiments of the invention, a footplate can rest on a ball joint and motion can be provided with two motors, as described, for example, with reference to FIG. 5.

Stress Analysis of Exemplary Robotic Platform Components

FIGS. 13-15 show further views of one or more embodiments of the invention. FIG. 13 shows an isometric view of a footplate assembly 1501 according to one or more embodiments of the invention. The footplate assembly 1501 can include an inner footplate 1502 and an outer footplate 1503, links 1504 interfacing the inner footplate 1502 and the outer footplate 1503, a frame 1505 (not shown), and links 1506 interfacing the outer footplate 1503 and the frame 1505 (not shown). FIG. 14 shows a top view of a footplate assembly 1601 according to one or more embodiments of the invention. The footplate assembly 1601 can include an inner footplate 1602 and an outer footplate 1603, links 1604 interfacing the inner footplate 1602 and the outer footplate 1603, a frame 1605 (not shown), and links 1606 interfacing the outer footplate 1603 and the frame 1605 (not shown). Based on testing an embodiment of the invention, a maximum deflection can occur, for example, at the location of the peak force 1507 and 1607 shown in FIG. 13 and FIG. 14, respectively. The maximum deflection can, for example, be approximately 0.275 millimeters in one or more embodiments of the invention. In an embodiment, the maximum allowable deflection that would be noticed by a user can, for example, be 2 millimeters. It can be desirable that a patient not feel deflection of the footplate under his/her weight and not experience a loss of confidence in the safety of a device. Since one or more embodiments of the invention can be used as medical devices and with patients experiencing balance issues, it can be desirable for a plate assembly to be strong enough to make the users feel comfortable and safe. With certain embodiments having, for example, 0.27 mm as the maximum deflection, these embodiments can, for example, provide a Factor of Safety (SF) of 7.4.

Stresses experienced in an embodiment of the footplate assembly were also assessed. FIG. 15 shows an isometric view of an footplate assembly 1701 according to one or more embodiments of the invention. The footplate assembly 1701 can include an inner footplate 1702 and an outer footplate 1703, links 1704 interfacing the inner footplate 1702 and the outer footplate 1703, a frame 1705 (not shown), and links 1706 interfacing the outer footplate 1703 and the frame 1705 (not shown). FIG. 16 shows a close-up of an example of a peak-stress location on a footplate assembly according to one or more embodiments of the invention. The footplate assembly 1801 can include an inner footplate 1802 and an outer footplate 1803, links 1804 (not shown) between the inner footplate 1802 and the outer footplate 1803, a frame 1805 (not shown), and links 1806 between the outer footplate 1803 and the frame 1805 (not shown). In an embodiment of the invention, the majority of the footplate assembly, as shown in 17, can, for example, experience less than 10.6 MPa. The location of peak-stress can occur in an embodiment of the invention, for example, on an AISI 1566 steel drive shaft as shown in 18 with a value of 47.6 MPa. In an embodiment of the invention, the allowable stress for acrylic, which can be the material of the center of the footplate, can, for example, be 48 MPa, and since the stress it experiences can be less than 10.6 MPa, such that the FS can, for example, be about 4.6 for this embodiment. For aluminum 6061, which can be the majority of the footplate assembly in this embodiment, the allowable stress can, for example, be 172.4 MPa, such that the FS can, for example, be 16 in this embodiment. Finally, a location of peak-stress can, for example, use AISI 1566 steel in an embodiment of the invention, which can, for example, have an allowable stress of 2.07 Gpa this embodiment. This means the FS can, for example, be 43.5 in this embodiment. However, a shaft can, for example, be 0.75 inch diameter in an embodiment of the invention due to high torque. The calculation for the shaft diameter can be based on the allowable stress of the shaft material and the applied torque in an embodiment of the invention.

$\sigma = \frac{TD}{21}$ $I = \frac{\pi \; D^{*}}{32}$

These two equations can be substituted into each other and simplified, with the diameter isolated. The following equation can result:

$D = \sqrt[s]{\frac{T \times 16}{\pi\sigma}}$

For example, using 2.07 GPa as an allowable stress and a torque of 210 Nm, in an embodiment of the invention, one such appropriate diameter can be found to be 0.008 meters, or 0.315 inches certain embodiments. The chosen shaft diameter can, for example, be 0.75 inches in an embodiment of the invention, which means there can, for example, be an FS of 2.38 in this embodiment. In certain embodiments, this can be a more realistic FS than, for example, 43.5 for the static analysis. If an embodiment were only experiencing static loads, then the shaft diameter could be much smaller, but since the limiting factor in this embodiment can be the stress produced by the dynamic torque, this calculation can be used to decide a shaft diameter in this embodiment.

Mechanical Stops

One or more embodiments of the invention can include safety precautions such as mechanical stops, which can be located underneath the footplate. Mechanical stops can act as a limiter to prevent over rotation of the footplate. In one or more embodiments of the invention, for example, the maximum rotation on the inversion/eversion axis can be 40° of rotation. Mechanical stops can be included in case the control system fails to stop the user at 40°. In other embodiments, the maximum rotation on the inversion/eversion axis can be greater than 40° of rotation, and in still other embodiments, the maximum rotation on the inversion/eversion axis can be less than 40° of rotation. The stops also can be lower to allow the rotation to go past a maximum angle so that the stops prevent motion after a control systems fails. FIG. 17 shows a stop 1907 for the inversion/eversion axis according to one or more embodiments of the invention in which the footplate assembly 1901 can include an inner footplate 1902 and an outer footplate 1903, links 1904 between the inner footplate 1902 and the outer footplate 1903, a frame 1905, links 1906 between the outer footplate 1903 and the frame 1905, and a stop 1907.

In one or more embodiments of the invention, a maximum rotation on the plantar/dorsiflexion axis can, for example, be 60° of rotation. In one or more embodiments of the invention, a stop on this axis can be built into the frame using a cross beam. The stop can, for example, be constructed from the 8020 or another material. FIG. 18 shows a stop for the plantar/dorsiflexion axis according to one or more embodiments of the invention in which the footplate assembly 2001 can include an inner footplate 2002 and an outer footplate 2003, links 2004 between the inner footplate 2002 and the outer footplate 2003, a frame 2005, links 2006 between the outer footplate 2003 and the frame 2005, and a stop 2006.

Stationary Platform

According to one or more embodiments of the invention, a stationary platform can be included. As shown in FIG. 2, a larger stationary platform 202 can enclose two robotic platforms 201. For some exercises, it may be desirable to have additional space for patients to practice taking steps and balancing at different orientations. As such, a larger stationary platform can provide additional space in the front of the robotic platforms or in other locations around the robotic platforms to allow additional space for patients to practice taking steps and balancing at different orientations.

One or more embodiments of the invention can include a stationary platform, which can provide structural support for the entire system. FIG. 1 shows a view of a Virtually-Interfaced Robotic Ankle and Balance Trainer system 100 according to an embodiment of the invention. The Virtually-Interfaced Robotic Ankle and Balance Trainer system 100 can comprise a stationary platform 101, and the stationary platform 101 can house two robotic platforms 102. Additionally, safety features such as safety rails 103 can attach to the stationary platform 101. The system 100 can also include a lift-assist chair device 104. In one embodiment of the invention, the platform can, for example, be 50″ wide×58″ long x 15.5″ tall (not including the railings). In other embodiments, the platform can be built to other dimensions. In an embodiment, there can be additional room in front of the robotic platforms to allow for additional exercises. In additional embodiments of the invention, there can, for example, be 18″ of platform space to allow for a step to be taken. In other embodiments, there can be other amounts of platform space. One or more embodiments of the invention can, for example, use 1.5″×1.5″ aluminum extrusions from 80/20 for a base frame to provide structural support and quick assembly. In further embodiments, other materials with other dimensions can be used to provide structural support. Additionally, in one or more embodiments of the invention, a base frame can be built in, for example, four separate parts for quick disassembly so it can be more easily moved.

Sliding Track

In one or more embodiments of the invention, a sliding track system for robotic platforms that can be included. The sliding track system can be attached underneath the stationary platform. Due to different anatomies, the comfortable stance width between two feet varies from person to person. A sliding track in accordance with one or more embodiments of the invention can allow for footplate subsystems to be adjustable. One or more embodiments of the invention an include fixed positions to ensure stability and prevent the footplates from shifting unintentionally. For one or more embodiments of the invention, the stance width can vary, for example, from six to sixteen inches. As such, in one or more embodiments of the invention, the track can provide for adjustability at every two inches. Of course in other embodiments of the invention, the spacing between the footplate subsystems can vary by other amounts and the spacing can be incremented by other amounts or can be adjusted continuously. By allowing for adjustment of the distance between the footplate assemblies, embodiments with a sliding track can provide a third degree of freedom, in addition to inversion/eversion and plantar/dorsiflexion.

In one or more embodiments of the invention, a foot plate and subcomponents can be placed on a track on the floor. FIG. 19 shows foot plate and subcomponents 2301 and tracks 2302. In one or more embodiments, mechanical stops can be added to for stability. A potential concern when the spacing between footplates can be adjusted may be gaps between the footplates where a user could fall or step into a gap, potentially causing injury. In one or more embodiments of the invention, this can be addressed with the use of attachable platforms to be placed in between the footplates.

Safety Features

For one or more embodiments of the invention, many the patients using the system may not have sufficient ankle balance and strength to use the device without additional safety features. For this reason, one or more embodiments of the invention can include handlebars, a safety harness, and/or other safety features.

Handle Bars

For one or more embodiments of the invention, handlebars such as curved railings 203 in FIG. 2 can allow for any person, no matter the height, to comfortably hold onto them while stepping onto the platform. Curved railings can also advantageously eliminate some or all sharp edges, which can improve patient safety in the event that a patient falls. The railing 204 in the front can be adjustable from, for example, three to four feet, or other amounts, to accommodate different patient heights.

In one or more embodiments, safety rails 203 can be included on top of the stationary platform, as shown in FIG. 2. Since patients can be at risk of losing their balance when performing exercise, the inclusion of safety rails in certain embodiments can advantageously provide structure for them to hold onto while exercising. In an embodiment of the invention, the design can utilize 1.5″ hollow-aluminum rods that provide standard rigidity for rails. “Slip-On” rail fittings can be used to allow for quick and easy assembly, while maintaining structural support to provide stability to the system. In one or more embodiments, the left, right, and front handle bars can be adjustable in height from 24″ to 40″ to accommodate the different patient heights. In other embodiments, the design can utilize different materials with different dimensions.

Harness

In one or more embodiments of the invention, a safety harness can serve to protect a patient if he or she were to lose his or her balance. A safety harness can also be used to bear some of the patient's weight. In certain embodiments, a safety it may be used as an unweighing safety harness. In one or more embodiments, a safety harness can be mounted directly onto the overall system and can be easily be attached or detached. FIG. 20 shows an example of a safety harness 2501, which can be used in accordance with one or more embodiments of the invention.

Foot Release Mechanism

In one or more embodiments of the invention, a foot release mechanism can be used to provide additional safety for a patient as well as to protect the components of the device. In one or more embodiments, a foot release mechanism can securely hold a patient's foot in place while operating under normal conditions and can release a patient if a patient falls or begins to exceed a max allowable torque on the device. Additionally, it may be desirable for the foot release mechanism to be low cost and simple.

Velcro™ or Button Strap

In one or more embodiments of the invention, a strap can be attached to the foot plate and can lay over the patient's foot to secure it to the foot plate. An advantage of such embodiments is the adjustability. Due to a wide range of the size of a patient's foot, the strap can easily be adjusted to fit the patient accordingly.

“Ski Binding Quick Release”

One or more embodiments of the invention can incorporate a foot release mechanism like a ski binding, where, when a large amount of torque is applied to the binding, the device can release the foot.

Chair

One or more embodiments of the invention can provide a chair system to allow a patient to perform exercises over a range of angular seated positions. For example, a stroke patient that has trouble standing may benefit from adjustable seating so that retraining muscle control can be performed over incremental positions between sitting and standing. In one or more embodiments of the invention, the rehabilitation device can provide training capabilities at a common seated position, as shown, for example, in FIG. 21 and standing, as shown, for example, in FIG. 22. Embodiments of the invention can provide an easy way for a user to attach a chair subsystem to the main platform, to sit comfortably in the chair, and adjust the height or angle as desired.

Chair on Moving Platform

One or more embodiments of the invention can include a chair 2601 on a standalone platform 2602 that can be wheeled up to a main platform and can be secured to it. The chair can be a basic off-the-shelf component in conjunction with a lift-assist seat pad (also off-the-shelf) placed on top of the chair that can electronically adjust to increase the seated angle from 0° up to 80°, for example, as can be seen in FIG. 21. In addition, for safety and comfort, a seatbelt can be included to secure around the waist of a user to keep the user from sliding off the seat pad when at an incline.

Rolling height-adjustable chair

One or more embodiments of the invention can use a chair 2901 that can include wheels on the bottom and can be wheeled directly up to the platform. In one or more embodiments, the chair 2901 can use a hydraulic pump system, similar to a barber chair. As shown in FIG. 23, the chair 2901 can be lowered so the patient can sit down and be secured via a seatbelt into the chair 2901. After being brought over to the platform, the chair height of chair 2901 could be raised using the foot pump until the patients feet can comfortably reach the robotic platform. Similar to depiction in FIG. 23, the chair 2901 device can have a lift-assist seat to adjust the patients seated angle during rehabilitation.

Transmission System

A robotic footplate according to one or more embodiments of the invention can provide controlled rotation, speed, and torque with accuracy and precision. Furthermore, in one or more embodiments of the invention, a robotic footplate can be controlled by a motor/gearbox combination for each degree of freedom, both in inversion/eversion and plantarflexion/dorsiflexion. Additionally, in one or more embodiments of the invention, a gearbox can provide torque amplification and speed reduction. Possible mechanical specifications according to one or more exemplary embodiments are summarized in Table 1 below.

TABLE 1 Possible mechanical specifications Plantarflexion/Dorsiflexion Configuration Specifications Rated Torque 230 N-m (2036 lb.-in) Speed 20-30 RPM Power 480-720 Watts Inversion/Eversion Configuration Specifications Rated Torque 64 N-m (567 lb.-in) Speed 15-20 RPM Power 100-135 Watts

Of course in other embodiments, different mechanical specifications can be used.

Exemplary Pulley and Timing Belt Selection

In one or more embodiments of the invention, the power from both the inversion/eversion and plantarflexion/dorsiflexion motors can be transmitted through the use of a timing belt, as discussed previously. Such embodiments can reduce or minimize backlash and misalignment issues. In one or more embodiments of the invention, the belt and pulley can provide torque and RPM from each motor. In one or more embodiments of the invention, the length of the belt can, for example, be selected based on the center distance between the driver and driven shaft. Exemplary input values and exemplary selected drive output for an exemplary embodiment can be seen in FIG. 24.

Exemplary Sensor Selection

In one or more embodiments of the invention sensors can be employed to supply feedback to motors for precise control. One type of feedback that can be provided is positional feedback of the footplate, which can be provided by an encoder. Another sensor that can be used in one or more embodiments of the invention is a pressure map system for measuring peak pressure on the foot in magnitude and location so that the torque output from the motor can be appropriate for a given patient's treatment regimen. A single force sensor on each footplate can also be used in one or more embodiments of the invention to provide a total weight of the patient. This information may also be used for determining a weight percentage distribution for different applications of the device.

Encoders

In one or more embodiments of the invention, an encoder can be placed on each motor shaft. In one or more embodiments of the invention, there can be an encoder on the footplate shafts for each rotational direction. If there is an error in the transmission of rotation between the motor and the footplate shaft, the error can be read between the two encoders on each degree of freedom.

An encoder can be used on both axes of rotation. A differential, optical rotary encoder can, for example, be used. An exemplary encoder can, for example, have resolution of 1,250 counts per revolution. In other embodiments, other encoders can be used. In one or more embodiments of the invention, for the inversion/eversion axis, the encoder can be directly mounted to the motor via a dual-shaft configuration. In one or more embodiments of the invention, for the plantarflexion/dorsiflexion motor, an encoder can be applied directly to the axis of rotation. In other embodiments, encoders can be attached in other manners.

Pressure Map

According to an aspect of the invention, in one or more embodiments, to provide peak pressure and center of pressure (COP) readings, a pressure mapping sensor can be employed. In one or more embodiments of the invention, a pressure map can be interfaced with a computer via a USB connection and an interface module. In other embodiments, other interfaces and connections can be used.

In one or more embodiments of the invention, pressure map measurements can be incorporated into a motor control system that, for example, uses Lab View or other software. In an embodiment of the invention, the pressure map software provided can also be used separately from motor control.

In one or more exemplary embodiments of the invention, a pressure map can, for example, provide readings up to 30 PSI or 206.84 kPa. In other embodiments of the invention, a different type of pressure map can be used. In addition, in an exemplary embodiment of the invention, the size of the pressure map can, for example, be 23 cm long and can, for example, be shaped like a foot. For other embodiments of the invention a higher or different value can be used, as well as other shapes. Additionally, in one or more embodiments of the invention, a custom size pressure map can be used.

Exemplary Support Frame of Robotic Platform

In an exemplary embodiment of the invention, as a result of finite element analysis, as well as calculations, materials for the support frame were selected to provide safe and effective operation with minimal deflection and minimal stress under maximum weight application. In one or more embodiments of the invention, the support frame of the robotic platforms can, for example, be aluminum. In one or more embodiments of the invention, the outer frame of the robotic platform can be robust and can precisely fit together. In further embodiments of the invention, other materials can be used for the support frame.

FIG. 25 shows a 3D CAD image of an exemplary robotic platform support frame 3300 according to one or more embodiments of the invention.

Interior Frames of Robotic Platform

In one or more embodiments of the invention, interior components of a robotic platform can be driven by a transmission system. Additionally, in one or more embodiments of the invention, two rectangular interior frames can be combined together such that they can each rotate around a different axis (providing 2 degrees of freedom motion), such as an inversion/eversion axis and a plantar/dorsiflexion axis. In one or more embodiments of the invention, an inversion/eversion frame can be located within a plantar/dorsiflexion frame. In one or more further embodiments of the invention, a plantar/dorsiflexion frame can be located within inversion/eversion frame. In one or more embodiments of the invention, an inversion/eversion frame can be part of a footplate, and in one or more further embodiments of the invention, a plantar/dorsiflexion frame can be part of a footplate.

FIG. 26 shows a sub-assembly of a rotating portion of a robotic platform according to one or more embodiments of the invention. In an embodiment of the invention shown in FIG. 26, a rotating portion of a robotic platform can comprise a footplate assembly 3401, which can include an inversion/eversion frame 3402 and a plantar/dorsiflexion frame 3403. As shown in FIG. 26, the inversion/eversion frame 3402 can be located within the plantar/dorsiflexion frame 3403. In other embodiments, a plantar/dorsiflexion frame can be located within an inversion/eversion frame. The robotic platform can further comprise, shafts 3404 and 3406. The shafts 3404 can be located between the inversion/eversion frame 3402 and the plantar/dorsiflexion frame 3403, and shafts 3406 can be located between the plantar/dorsiflexion frame 3403 and a support frame 3405 (not shown). In other embodiments, other arrangements can be used. For example, in one or more embodiments, the shafts 3406 can be located between the inversion/eversion frame 3402 and the plantar/dorsiflexion frame 3403, and shafts 3404 can be located between the plantar/dorsiflexion frame 3403 and a support frame 3405 (not shown). The robotic platform can further include supports 3407, which can reinforce the footplate assembly 3401.

In one or more embodiments, an inversion/eversion frame can rotate around two shafts, as, for example, shown in FIG. 26. A challenge with fabricating components for an inversion/eversion frame can be alignment. In an embodiment of the invention, a single shaft through the whole length of a footplate can be used. In such an embodiment, a more precise fabrication process can be used for proper rotation. In an embodiment, two separate shafts can be used to mitigate twist that can be seen in a drive shaft by making the shaft shorter. For one or more embodiments of the invention, it may be desirable to use a process of machining/fabricating these parts with high accuracy, for example, within one-thousandth of an inch (0.001″), to help provide proper alignment. A further potential challenge for an inversion/eversion frame such as the one depicted in FIG. 26 can be alignment issues with screw holes. For example, in an exemplary embodiment, screw holes can be located at the corners of aluminum bars that can be used for a frame structure. For one or more embodiments of the invention, adjustments can be made to the width of ledges on either end such that holes line up. Such adjustments can be an part of the fabrication process. In one or more embodiments of the invention, the frame can be square to prevent contact with a support frame during rotation. In other embodiments of the invention other structures can be used to provide inversion/eversion rotation and plantar/dorsiflexion rotation. Such structures can use a variety of shapes and constructions and are not limited to the exemplary embodiments shown, for example, in FIG. 26.

In one or more embodiments of the invention, a footplate on which a user stands can be made of acrylic to decrease the weight of the moving components. In other embodiments of the invention, other materials can be used to construct the footplate. In one or more embodiments of the invention, bars, which can be made of steel and/or other materials, can be incorporated into the design, for example as horizontal supports under the acrylic, to minimize the deflection experienced by the acrylic alone. In further embodiments of the invention, vertical supports or supports with any other orientation can be used. FIG. 27 shows an image of an interior frame inversion/eversion sub-assembly 3501 according to one or more embodiments of the invention, which can comprise an inversion/eversion frame 3502 and shafts 3504, which can be located between the inversion/eversion frame 3502 and a plantar/dorsiflexion frame 8353 (not shown), and supports 3507. In other embodiments, other configurations can be used. For example, an inversion/eversion frame can be an outer frame, and shafts 3503 can be located between the inversion/eversion frame and a support frame or other structure.

According to an aspect of the invention, in one or more embodiments, cutouts or other structures for locking pins or other locking mechanisms can be included to lock the position of the footplate for operation in a stable mode. In one or more embodiments of the invention, an acrylic footplate and steel supports can be mounted to an inside frame, which can comprise bars. In one or more embodiments, there can, for example, be four bars, which can be made of aluminum and/or other materials. In one or more embodiments, the bars can include cutouts for locking pins for stable mode. For example, FIG. 27 shows holes 8308, which can be used as cutouts for locking pins for stable mode. In one or more embodiments of the invention, there can also be cutouts in two side aluminum bars, such that steel bars and an acrylic plate can be flush with the top of the aluminum bars.

In one or more embodiments, an inversion/eversion frame and/or a plantar dorsiflexion frame, which can be inner frames or outer frames, can be constructed, for example, using four aluminum bars. In one or more embodiments, such aluminum bars can be designed to fit each other at each corner without significant overlap or room to shift. In one or more embodiments, these parts can be secured with two 8-32 socket head fasteners at each corner of the aluminum frame and along the sides of the acrylic footplate to secure it to the steel supports and the aluminum frame. In other embodiments, components of an interior frame, such as an inversion/eversion sub-assembly or a plantar/dorsiflexion subassembly, can be constructed with other materials and combinations of materials and can use other attachments.

In one or more embodiments of the invention, a plantar/dorsiflexion frame can rotate around an axis perpendicular to that of an inversion/eversion frame. FIG. 28 shows an image of an interior frame plantar/dorsiflexion frame sub-assembly 3601 according to one or more embodiments of the invention, which can comprise a plantar/dorsiflexion frame 3603, shafts 3604, and shafts 3606. The shafts 3604 can be on the ends and can be for inversion/eversion. In one or more embodiments of the invention, the shafts 3604 can pass through the plantar/dorsiflexion frame to reach a pulley system that can be driven by the motor and gearbox. The shafts 3606 can be on the side and can be for plantar/dorsiflexion rotation. In one or more embodiments of the invention, a shaft 3604 can be keyed at the end and can attach to a pulley after passing through a mounted bearing. The shaft 3604 at the other side that can be not keyed at the end and can fit into a mounted bearing and can keep the plate horizontal for alignment and add support. As with an inversion/eversion frame sub-assembly, potential fabrication/machining concerns with these components can include shaft alignment and hole alignment, but these problems can be avoided with precise machining, accurate measurements, and/or other alignment techniques.

In an exemplary embodiment, the plantar/dorsiflexion frame 3603 can use two 8-32 socket head fasteners at each corner of aluminum bars such that the components of a rectangular assembly can stay at substantially 90° to each other. In other embodiments, the plantar/dorsiflexion frame 3603 can be constructed from other materials and structures and can use other fasteners.

Transmission System Assembly

In one or more embodiments of the invention, a pulley and timing belt assembly can be used to drive shafts from motors. In an exemplary embodiment of the invention, the ratio of a drive pulley to a driven pulley can, for example, be 1:1. In other embodiments, other ratios can be used. In one or more embodiments of the invention, a gearboxes can provide a mechanical advantage and pulleys can, for example, be kept at the same radius for each respective degree of freedom system. In one or more embodiments of the invention, a sprocket of the pulley assembly can, for example, be mounted to a coupler, which can fit on to a steel drive shaft, and the transmission of force can be through a key.

One or more embodiments of the invention can provide an appropriate tension to the belt such that there is little or no slippage or backlash when high forces/torques are experienced, which can provide for safe and precise operation of a pulley and timing belt assembly. This tension can be provided, for example, by an idler pulley that can be installed on both inversion/eversion and plantar/dorsiflexion drive systems. An exemplary idler pulley for the plantar/dorsiflexion timing belt according to one or more embodiments of the invention is shown in FIG. 29. In an exemplary embodiment, an idler pulley can be included for the plantar/dorsiflexion timing belt to tension it to 50 pounds, for example, or to another tension. In an exemplary embodiment, for the inversion/eversion timing belt, an idler pulley can be used to tension it to 20 pounds, for example, or to another tension.

System Controls

In one or more embodiments of the invention, the system can be controlled by a controller system controlling the motor. In one or more embodiments, each motor can have its own controller to control its movement. In an exemplary embodiment, software and a controller can, for example, be used. Table 2 shows exemplary input specifications for each motor in an exemplary embodiment of the invention.

TABLE 2 Exemplary input specifications for each motor in an exemplary embodiment Input PFDF Motor INEV Motor Rotor Inertia (oz-in-s²) 0.03399 0.01133 No. of Poles 8 8 Peak Torque (oz.-in) 900 297 Rated Torque (oz.-in) 297 Velocity Limit (RPM) Torque Constant (oz.-in/A) 17 53.8 Back EMF Volt. (V/kRPM) 11.5 29.5 L2L Resistance (ohms) 0.16 3.8 L2L Inductance (mH) 0.3 10.95

In an exemplary embodiment of the invention, motor position can be controlled, for example, with the software using internal sensors.

In one or more embodiments of the invention, encoders can be used to control each motor and, as such, to control rotation of a footplate. In an exemplary embodiment, an encoder can, for example, be integrated into software control for each motor. In an exemplary embodiment of the invention, once control of the motor was established using, the software was eliminated and the controller was controlled by LabVIEW. 38 shows an exemplary plantarflexion/dorsiflexion controller using a dial in the control window according to one or more embodiments of the invention.

In one or more embodiments of the invention, a controller can be integrated into the system to control both motors at the same time. For an exemplary embodiment of the invention, after the LabVIEW program was complete for each individual motor, a physical controller was integrated into the system to control both motors at the same time. For this mode, the user can, for example, control the position of the footplate with a joystick controller or other controller. Both inversion/eversion and plantarflexion/dorsiflexion can be controlled, for example, with a single remote. FIG. 31 shows a block diagram depicting the flow of information from the user's hand to the position of the footplate in one or more embodiments of the invention. In an exemplary embodiment, a joystick position can be read by LabVIEW and can be converted to a corresponding voltage, and a motor controller can output this voltage to the motor and gearbox which can rotate the footplate.

In an exemplary embodiment, the footplate position can be read by the encoder, and an angular position read by an encoder can be displayed, for example, in a LabVIEW program. FIG. 32 shows an exemplary LabVIEW control window according to one or more embodiments of the invention. There can be two inputs in the controller: a mouse to turn the motor on/off and a joystick to control the position. The input voltage for each motor can have a numerical display. A graphical output of each direction can also be shown. In other embodiments, other inputs and configurations can be used to measure a position of the footplate.

In one or more embodiments of the invention, the control of the system can be a closed loop, limiting the angular range of each direction to specifications. A software “stop” can prevent the user from rotating a footplate past an acceptable limit. Additionally, as noted previously, mechanical stops can also be included in one or more embodiments.

Clinical Exercises and Control Design

In one or more embodiments of the invention, the system can include controls for clinical exercises. Table 3 lists examples of some of the clinical exercises and stretches that one or more embodiments of the invention can be configured for a patient to perform.

In one or more embodiments of the invention, the device can have the capability to operate in various modes. Depending on the mode, the motor control can vary. Additionally, some exercise can have the option to be run in multiple modes. One or more embodiments of the invention can include the modes described in Table 4.

TABLE 4 Device modes and control design notes Control Mode Description Design Notes Diag- In this mode the device can allow the user A measurement nostic to run through their ROM and can give the system for ROM therapist information on the severity of and strength injury. This will include their strength and can be used. flexibility. Assis- The device can assist the user in completing A patients foot tive a desired motion. This can be for users should not be entering therapy that do not have the moved too strength or flexibility to complete the quickly, this may exercise. cause spasticity. Pas- The device only compensate for its own Programming can sive weight, giving the effect that the patient's account for foot is not attached to anything; they can motor and foot- complete the exercise by their own will. plate weight so the user is not being weighed down by them Resis- For more advanced users the device can Forces should not tive resist the users motion in a similar manner be too high as to a band, making the exercise more to strain the difficult. users foot. Haptic This mode can be used to train the users Pathway muscle do perform a correct motion path. boundaries This can be done, for example, in assistive, can be defined. passive, or resistive modes. As the user deflects from the path of motion the device can resist their motion, correcting the pathway. Balance In this mode, the platforms can be locked The center of into position and the pressure maps can be pressure can be used to locate the users center of pressure. calculated. The user can then practice shifting their weight to change their center of pressure.

Frame Resizing to Reduce the Stance Width

In one or more alternative embodiments of the invention, the footplate and rotating frames can have reduced size to reduce stance width. After an initial build of the two robotic platforms according to an exemplary embodiment of the invention, it was decided that it was desirable to provide one or more embodiments where the overall stance width can be narrower. A smaller version of the platforms according to one or more embodiments was first modeled in CAD to determine where material could be removed. In one or more embodiments, the footplate can be narrower and the gaps in between each plate can be made smaller, and the shafts in the bearings can be cut down.

For an exemplary embodiment, an FEA analysis with was completed. Models for isometric stress, maximum stress, and deformation were created for a 3001b load at the ball of the foot and in the center of the footplate. FIG. 33 is an example of one of the FEA models and Table 5 shows the results for each model according to an exemplary embodiment of the invention. FIG. 33 shows exemplary deformation due to loading on the ball of the foot on resized frame according to one or more embodiments of the invention.

TABLE 5 Exemplary results of FEA analysis on the resized frames. All results are maximum values for exemplary embodiment. Load Applied to: Iso Stress (Pa) Max Stress (Pa) Deformation (m) Ball of Foot 5.148e8 5.148e8 6.85e−4 Center of Plate 7.214e8 7.214e8 8.74e−4

In an embodiment of the invention, each piece of the outer frame and footplate that contributes to the width of the device can be cut down. Both platforms in an embodiment of the invention can be taken apart, cut down, and reassembled. To reduce the gap width in-between inversion/eversion and planter/dorsiflexion footplates, in one or more embodiments of the invention, the cap heads 4201 on the shafts 4202 can be countersunk into the frame 4203. FIG. 34 shows an example cap heads 4201 of shafts 4202 counter sunk into a frame 4203 according to one or more embodiments of the invention. In one or more embodiments, such changes can reduce the overall stance width down to approximately 12 inches. In one or more embodiments, the platforms can be adjusted for a wider or narrower stance width.

Load Cell Implementation

In one or more embodiments of the invention, sensors can be used to measure the tension and compression applied to the footplate by the user for feedback control for the platform. Because of the desirability of providing a tension reading when a foot is in dorsiflexion and other orientations, in one or more embodiments of the invention, load cells can be used under a footplate. FIG. 35 shows an example of load cell 4301 placement according to one or more embodiments of the invention. In one or more embodiments of the invention, four load cells 4301 can be placed under four screws 4302 on a footplate 4303.

FIG. 36 shows an example of a crossbar 4403 for mounting load cells 4401 and springs 4402 according to one or more embodiments of the invention. In one or more embodiments of the invention, to measure tension with the compression load cells 4401, a pre-load can be applied using mechanical springs 4402. The load cells 4401 can be attached, for example, to a custom machined crossbar 4403 under a platform 4404.

In one or more embodiments of the invention, a sandwich configuration can be used to preload load cells 4501, an example of which is shown in FIG. 37. The load cells 4501 can be attached to a cross bar 4503 and then sandwiched by an upper plate 4505. A bolt 4506 can be inserted through the cross bar 4503 and upper plate 4505 and secured above the plate 4505 by a bolt 4506, which can be covered by the footplate 4504. In between the bolt head/washer 4507 and the crossbar 4503 can be a compression spring 4502.

In one or more alternative embodiments of the invention, the design can be fully adjustable for a desired preload. For example, tightening the bolt puts can put a compression load onto the load cells 4502, which can be manually adjusted for a desired preload on each load cell. In one or more alternative embodiments of the invention, there can be one spring 4502 for two load cells 4501. In one or more alternative embodiments of the invention, there can be a total of two springs 4502 and four load cells 4501. In other embodiments of the invention, any other numbers of springs and any other number of load cells can be used.

In one or more embodiments of the invention, spring selection can be based, for example, on overall length, deformation percentage, and/or the spring error. In an exemplary embodiment of the invention, a spring can, for example, have a length of approximately 1 inch. In an exemplary embodiment of the invention, a deformation in the spring can, for example, be greater than 33% of the overall length due to the spring mechanics. In an exemplary embodiment of the invention, the approximate movement to the spring because of the load cells can, for example, be 0.001 inches, which can be the error in the preload.

Table 6 shows spring characteristics and calculations for exemplary springs in one or more embodiments of the invention.

TABLE 6 Exemplary spring selection. Total pre-load force 200 lbs. # Load Cells 4 qty Pre-load per load cell 50 lbs. # Springs 2 qty Load per spring 100 lbs. Length 1.00 in Calc def. length 0.18 in K 564.00 lbs./in Deflection % 17.73% Spring Error 0.56 lbs. Spr. Error %  0.56%

Springs can be assembled onto a device built according to an embodiment of the invention and can be tightened to apply a preload, for example, a 50 pound preload, on each load cell. In further embodiments of the invention, preloads of amounts other than 50 pounds may also be applied.

In one or more embodiments of the invention, such as a four load cell configuration, a device according to an embodiment of the invention can indicate a center of a pressure map. A patient's foot can be on a platform, and a red dot can be displayed in a LabVIEW interface and can show where the center of pressure is on the platform. Both platforms can be censored such that a center of pressure calculation can be an overall center of pressure of the user, in addition to or instead of a single foot. In one or more embodiments of the invention, a center of pressure measurement can be used for the balance exercises and can also be implemented with a game.

Encoders

In one or more embodiments of the invention, an inversion/eversion encoder and a plantar/dorsiflexion encoder can be used to measure inversion/eversion and plantar/dorsiflexion of a footplate. In one or more embodiments of the invention, an inversion/eversion encoder can be built into the back of an inversion/eversion motor, and a plantar/dorsiflexion encoder can be placed onto an outer shaft and can directly measure the actual angle of the footplate. In other embodiments of the invention, inversion/eversion encoders and plantar/dorsiflexion encoders can be located in other locations. For example, as shown in FIG. 38, in one or more embodiments of the invention, an inversion/eversion encoder 4601 be located on a shaft 4602. The shaft 4602 can attach to a drive belt 4603 and can be turned down and a cover 4604 can be included. The cover 4604 can house the encoder 4601. The cover can be constructed, for example, using a 3D printer.

In one or more embodiments, absolute encoders can be used for acquiring data. In other embodiments, other encoders may be used.

Inversion/Eversion Motor Cover

In one or more embodiments of the invention, an inversion/eversion motor can be completely enclosed, which may advantageously improve patient safety. FIG. 39 shows a CAD design of a cover 4701 on a motor 4702 according to one or more embodiments of the invention.

In one or more embodiments of the invention, a slant can be included in a front face of a cover, which may advantageously avoid a patients ankle or heel being affected by the cover. FIG. 40 shows a slant 4802 in a cover 4801 according to one or more embodiments of the invention. Advantageously, such embodiments can help avoid obstructing the users motion, for example, when used in a seated mode.

Surrounding Platform and Chair

According to an aspect of the invention, the device can include a platform and railing. In one or more embodiments of the invention, the platform can allow for a patient to train one leg at a time. In one or more embodiments of the invention, the platform can have enough room for a patient to take a step forward during training The platform can also have a rail system for patient safety. The rail system can be made of a material such as aluminum. One or more embodiments of the invention can include sliding rails that allow for adjustability to patient height. The extension of the rails can also allow a patient to use the railings while getting up on the platform. FIGS. 41 and 42 show views of a CAD model of a platform and rail system according to one or more embodiments of the invention. In FIG. 41, an embodiment of the invention comprises surrounding platform 4901, rail system 4902, and robotic platform 4903. In FIG. 42, an embodiment of the invention comprises surrounding platform 5001, rail system 5002, and robotic platform 5003.

In one or more embodiments of the invention, the platform base can be made out of a material such as 80-20. The robotic platform can also be made out of similar material for ease of assembly. The railings can be made out of a material such as aluminum piping to make it more stable and keep it relatively lightweight. In further embodiments, other materials can be used for these features.

In one or more embodiments of the invention, the chair design can be modeled as a bench. In one or more embodiments, a bench can account for different patient leg lengths as well as motors on the back of a device and bring a patients foot close enough for training A bench can also be adjustable in height and can be on wheels so that a patient can be moved over a platform according to one or more embodiments of the invention. FIG. 43 shows a CAD design for a bench 5101 according to one or more embodiments of the invention. The bench 5101 can be made out of any material. For example, in one or more embodiments of the invention, the bench 5101 can be constructed out of metal and/or wood. In one or more embodiments of the invention, the bench 5101 can be separate from a frame 5102 and can be removable. One or more embodiments of the invention can further comprise platforms 5103, which can, for example, be 31 inches by 18 inches by 16 inches, or any other dimensions.

In one or more embodiments of the invention, a platform can be controlled with a hand-held remote control. FIG. 44 shows an embodiment of the invention, which can comprise robotic platforms 5201 and a remote control 5202.

In one or more embodiments of the invention, patients can be seated and can play a simple game, such as a maze game. Additionally, patients can perform tasks such as an isometric strength task and a free ankle movement task at various speeds. One or more embodiments can further include a chair and foot strap as discussed previously.

Static Force Measurement

In one or more embodiments of the invention, an ankle and balance rehabilitation system can measure human interaction force. For example, one or more embodiments of the invention can include four compression load cells installed in the footplate and can include a unique mechanical design such that both tensile and compressive loads can be measured. One or more embodiments of the invention can include load cells calibrated separately and can include load cells preloaded in pairs.

Mechanical Design

FIG. 45 shows top view A, a CAD drawing, side view B, and a top view C of a robotic force-plate according to one or more embodiments of the invention. As shown in FIG. 45, in one or more embodiments of the invention, a force-plate can include five different layers: four compression load cells 1, an acrylic footplate 2, a metal plate 3, two metal crossbars 4, surrounding aluminum beams 5 that can be connected to a system ground, and the linear spring 6 that can create a preload. A patient's foot can be strapped on the acrylic plate 2. Four load cells 1 can be inserted symmetrically in the four corners of the footplate, in between the metal plate 3 and metal crossbars 4. The metal crossbars 4 can be connected to the surrounding aluminum beams 5, which can be connected to system body. Load cells 1 can be placed in the Anterior(A)/Posterior(P) and Medial(M)/Lateral(L) planes with respect to the human ankle.

In one or more embodiments of the invention, a footplate can be composed of two layer rectangular plates: an acrylic and a metal plate. In an exemplary embodiment, the footplate can, for example, be 36.3 cm×16.2 cm (14 5/16 feet×6⅜ feet) and can, for example, weigh 2.295 Kg. In certain embodiments of the invention, acrylic can be lighter than metal and can provide a relatively high rigidity. In one or more embodiments of the invention, the metal plate can be attached to the acrylic plate to support and strengthen the footplate and to reduce deflection. Plastic shimmer paper can be used in between the plate and two specific load cells to compensate for an uneven metal surface. FIG. 46 shows a force-plate structure in accordance with one or more embodiments of the invention, which can comprise an acrylic plate 5401 connected to the metallic plate 5402. In one or more embodiments of the invention, shimmer papers can be used in between the footplate and AL and PM load cells to further even the contact.

In one or more embodiments of the invention a force plate can include load cells for force and pressure measurements. In one or more embodiments of the invention, four compression load cells can be inserted in a sandwich configuration in between a footplate and a system body or a mechanical ground. A tensile force measurement can be achieved by utilizing a preload configuration. FIG. 47 shows a mechanism of tensile force measurement in accordance with one or more embodiments of the invention, which can comprise springs 5501, which can create a preload on load cells. In one or more embodiments of the invention, a spring 5501 can be used for pairs of load cells in the anterior and posterior plane of the footplate. In an exemplary embodiment, the spring 5501 can, for example, have k≈10000 N/m. In other embodiments, springs with other k values can be used. The spring 5501 can be inserted in between a bolt head/washer 5502 and a metal crossbar 5503 below a force-plate 5504. A bolt can be screwed into a nut which can be welded on top of the footplate. In other embodiments, other arrangements can be used to apply a preload to load cells and to measure force and pressure.

In one or more embodiments of the invention, the amount of preload on each pair of load cells can be adjusted by tightening/loosening bolts. The preloaded force measurements can, for example, be set to zero and consequently a subject's dorsiflexion, for example, can relax the load cells and lead to tensile (negative) force measurements. In one or more embodiments of the invention, an applicable load to the springs can, for example, be 600 N, and the anterior and posterior springs can be preloaded, for example, by 220 N and 390 N respectively. In further embodiments of the invention, the springs can be preloaded with other values. In still further embodiments, these values can be acquired experimentally, which can improve accuracy in force measurement.

Load Cells

In one or more embodiments of the invention, four compression load cells can be used to measure a subject's interaction forces with the footplate. The load cell signals can, for example, be amplified and sampled into a desktop computer by, for example, using an NI PCI 6251. FIG. 48 shows a flow chart representing an exemplary collection of load cell data in accordance with one or more embodiments of the invention. Load cell signals can, for example, further be amplified and converted to digital. In one or more embodiments of the invention, each load cell can, for example, be connected to a corresponding external amplifier and analog channel on data acquisition board.

In one or more exemplary embodiments of the invention, load cells can, for example, produce 10 my output (2 mV/V×5 V excitation voltage) at a full load condition (e.g., 226 Kg). Using a built-in potentiometers, amplifier gain can, for example, be adjusted to 1000 (to create a 10 V output) and the offset voltage can be removed. Considering, for example, a 16-bit data acquisition board, in an embodiment of the invention, a minimum load resolution can, for example, be estimated as 3.5 g.

In one or more embodiments of the invention, load cells can be calibrated independently, for example, using an Instron machine, which can be used to provide test loads. FIG. 49 shows an example of load cells calibration characteristics in accordance with one or more exemplary embodiments of the invention. In accordance with one or more exemplary embodiments of the invention, FIG. 49 shows an example of a response of an exemplary individual load cell to exemplary applied loads provided, for example, by Instron machine. Test loads can be applied to the load cells and the output voltages can be recorded.

In one or more embodiments of the invention, load cells can be placed in the Anterior(A)/Posterior(P) and Medial(M)/Lateral(L) planes with respect to the human ankle As shown in FIG. 49, in one or more exemplary embodiments of the invention, six ascending test loads followed by 5 descending points, for example, can be considered to calibrate each load cell (e.g., 11 points in total). A curve fitting procedure can, for example, be conducted to find a best linear estimate (e.g., R²>0.998) for each load cell and acquired equations can, for example, be used to represent the corresponding load cells.

Force-Plate

In one or more embodiments of the invention, four load cells can be placed in between a footplate and a system ground to create a force-plate. Such embodiments can provide for measuring tensile and compressive loads. The force-plate can be used to measure total force and center of pressure (COP).

In one or more embodiments of the invention, load cells can have estimated linear curves that can be used to convert a voltage readings to force values. A LabVIEW program, for example, can be used to read load cell data from a data acquisition board and represent the values in a computer. In one or more embodiments of the invention, a Virtually-Interfaced Robotic Ankle and Balance Trainer can be equipped with four load cells under a rectangular footplate to measure both compressive and tensile forces. Load cells can be calibrated separately (e.g., out of the system) and mounted into the platform. A center of pressure and a total applied force to the force-plate can be acquired to evaluate the accuracy of a platform.

In one or more embodiments of the invention, a rectangular metallic plate in contact with four load cells may not perfectly straight and smooth. As such, shimmer papers can be used in addition to unequal preloads (e.g., 220 N vs. 390 N) to reduce unbalanced contact and provide more even interaction between a footplate and load cells. In certain embodiments, higher preload in the posterior plane can result in more accurate force measurements.

Load cell calibrations can demonstrate a strongly linear profile. Applied test loads can, for example, have a radius of 1.4 cm, which can limit accuracy evaluation in center of pressure. In one or more embodiments of the invention, point loads can be applied to the force-plate. Additionally, in one or more embodiments of the invention, the error in center of pressure under both loads can, for example, be less than 1.4 cm across the force-plate. The total applied force to the force-plate can, for example, also show less than 5% mean value in certain embodiments.

Rehabilitation Exercises

In one or more embodiments of the invention, a force-plate can be used in any type of static force and center of pressure measurement. Human subjects can, for example, be instructed to stand on a force-plate and play an ongoing virtual reality game, which can be driven by the center of pressure and total applied force to the footplate.

One or more embodiments of the invention can be used for a variety of exercises for rehabilitating a patient. For example, one or more embodiments of the invention can be used for minimal resistance exercises. For such exercises, an embodiment of the invention can measure range of motion in four directions and in circular movements. Additionally, one or more embodiments of the invention can be used for maximum strength exercises. For such exercises, an embodiment of the invention can allow a patient to exert maximum force in different directions and can measure the force asserted. Further, one or more embodiments of the invention can be used for 20% of maximum through range of motion exercises. For these exercises, an embodiment of the invention can allow a patient to exert approximately 20% of his or her maximum exertion through a range of motion and can determine a fatigue point.

One or more embodiments of the invention can be used for a variety of balance exercises. For example, one or more embodiments of the invention can be used in a locked mode for proactive balance exercises. One or more robotic footplates in accordance with one or more embodiments can be locked in position and a patient can, for example, shift his or her weight. The robotic platform can detect the weight shift using the force plate and can provide visual feedback, for example, through a virtual reality interface. Additionally, other balance tests such as a Romberg test can be performed by a center of pressure measurement from an embodiment of the invention to detect a weight shift and to provide feedback. One or more robotic footplates in accordance with one or more embodiments can also be unlocked for reactive balance training. For example, the inversion/eversion and plantar/dorsiflexion position of one or more footplates can be adjusted and center of pressure measurements can be made with one or more force plates.

In one or more embodiments of the invention, measurements can be provided by the force plate load cells and from angular potentiometers during ankle movements. Virtual reality training scenes can use force and motion data from ankle movements to interactively control a cursor within a maze-like game environment.

In one or more embodiments of the invention, patients can be tested in the seated position, with knee and ankle at 90 degrees, and the tested foot resting on the force plate of the device. A strap can be used to hold the ankle to the footplate. Isometric strength of dorsiflexor, plantarflexor, inverter and everter muscle groups can be tested with the footplate axes locked in a stable mode. Additionally, the anterior-posterior and medial-lateral axes of the footplate can be unlocked in a dynamic mode and ankle motion measures can be taken. Angular excursion of the ankle joint in each direction can be measured, for example at natural, self-selected and at fast-paced, but self-selected speeds. A patient's individual measured values for isometric force, movement excursion and movement velocity can then be used to customize input thresholds to move a cursor in various virtual reality games.

In one or more embodiments, virtual reality games can use the ankle isometric force control. In further embodiments of the invention, virtual reality games can use ankle motion/velocity control. In one or more additional embodiments, multiple levels of difficulty can be tested for each type of game. In further embodiments of the invention, resistive forces can be applied during testing. Additionally, in further embodiments of the invention, testing can be performed with the patient standing.

It will be appreciated that while a particular sequence of steps has been shown and described for purposes of explanation, the sequence may be varied in certain respects, or the steps may be combined, while still obtaining the desired configuration. Additionally, modifications to the disclosed embodiment and the invention as claimed are possible and within the scope of this disclosed invention. 

1. A robotic ankle and balance training platform comprising: a footplate to support a foot, said footplate capable of rotation about an inversion/eversion axis and a plantar/dorsiflexion axis; and an actuation system configured to apply: an assistive inversion/eversion force and a resistive inversion/eversion force to the footplate; and an assistive plantar/dorsiflexion force and a resistive plantar/dorsiflexion force to the footplate.
 2. The robotic ankle and balance training platform of claim 1, further comprising: an inversion/eversion frame to allow rotation of the footplate about the inversion/eversion axis; and a plantar/dorsiflexion frame to allow rotation of the footplate about the plantar/dorsiflexion axis.
 3. The robotic ankle and balance training platform of claim 2, wherein one of the inversion/eversion frame and the plantar/dorsiflexion frame are integral with the footplate.
 4. The robotic ankle and balance training platform of claim 1, further comprising: sensors for measuring at least one of tensile force, compressive force, and footplate position.
 5. The robotic ankle and balance training platform of claim 4, wherein sensors comprise: at least one pair of load cells; and at least one spring configured to assert a preload on the at least one load cell pair.
 6. The robotic ankle and balance training platform of claim 5, wherein the sensors comprise two load cell pairs and two springs and the load cells are located in the Anterior(A)/Posterior(P) and Medial(M)/Lateral(L) planes with respect to the ankle supported on the footplate.
 7. The robotic ankle and balance training platform of claim 4, wherein: the sensors are capable of measuring a center of pressure on the footplate.
 8. The robotic ankle and balance training platform of claim 4, wherein: the sensors are capable of measuring at least one of the assistive inversion/eversion force, the resistive inversion/eversion force, the assistive plantar/dorsiflexion force, and the resistive plantar/dorsiflexion force.
 9. The robotic ankle and balance training platform of claim 1, wherein the plantar/dorsiflexion axis is offset between approximately 20% and 40% of a length of the footplate from an end of the footplate.
 10. The robotic ankle and balance training platform of claim 1, further comprising: a mechanical stop to physically limit at least one of inversion/eversion and plantar/dorsiflexion movement of the footplate.
 11. The robotic ankle and balance training platform of claim 2, further comprising: a first pair of shafts substantially aligned with the inversion/eversion axis, wherein capheads on the first pair of shafts are counter sunk in the inversion/eversion frame; and a second pair of shafts substantially aligned with the plantar/dorsiflexion axis, wherein capheads of the second pair of shafts are counter sunk in the plantar/dorsiflexion frame.
 12. The robotic ankle and balance training platform of claim 1, wherein the actuator system further comprises: at least one of an inversion/eversion motor and a plantar/dorsiflexion motor.
 13. The robotic ankle and balance training platform of any of claims 12, wherein the at least one motor comprises: a pulley assembly; a gearbox to transfer force to the footplate via the pulley assembly.
 14. The robotic ankle and balance training platform of claim 1, further comprising: an encoder positioned to read at least one of an inversion/eversion position of the footplate and a plantar/dorsiflexion position of the footplate.
 15. A robotic ankle and balance training device comprising: a robotic first ankle and balance training platform according to claim 1; a robotic second ankle and balance training platform according to claim
 1. 16. The robotic ankle and balance training device of claim 15, further comprising: a controller for determining a desired force for at least one of the assistive forces and the resistive forces and instructing the actuator system of at least one of the robotic platform to provide the desired force to the footplate of the at least one of the robotic platforms.
 17. The robotic ankle and balance training device of claims 16, further comprising: a sliding track, wherein the sliding track is configured to allow a distance between the first and second robotic platforms to be adjusted.
 18. The robotic ankle and balance training device of claim 14, further comprising: a stationary platform to house the first and second robotic platforms; a safety rail connected to the stationary platform; a lift-assist chair to allow use of the first and second robotic platforms in a seated or a standing position; and a virtual reality interface configured to interface with the first and second robotic platforms and provide feedback in response to at least one of a footplate orientation and a force asserted by the foot.
 19. The robotic ankle and balance training device of claim 18, wherein at least one of the robotic platforms actuates in response to at least one of the force asserted by the foot and the feedback from the virtual reality interface.
 20. The robotic ankle and balance training device of claim 18, wherein the virtual reality interface is configured to provide visual feedback in response to a center of pressure measurement to at least one of the robotic platforms.
 21. A method of ankle and balance training comprising: measuring a range of motion of an ankle in at least four directions and in a circular motion using a robotic ankle and balance training platform; measuring a maximum exertion of the ankle in at least the four directions using the robotic platform; determining a fatigue point of the ankle at approximately 20% of the maximum exertion using the robotic platform; and detecting a weight shift of a patient using the robotic platform.
 22. The method of ankle and balance training of claim 21, wherein the weight shift is detected while a footplate of the robotic platform is stationary.
 23. The method of ankle and balance training of claim 22, wherein the weight shift is detected while a footplate of the robotic platform is rotating about one or more of an inversion/eversion axis and a plantar/dorsiflexion axis.
 24. A method of ankle and balance training comprising: placing a foot on a robotic ankle and balance training platform of claim 1; and receiving a visual feedback from a visual interface based on at least one of an orientation of the foot on the robotic platform and a force asserted by the foot against the robotic platform. 